Although many people expected Apple to follow last year’s pattern and release a developer preview of OS X 10.9 early this year ahead of a summer public launch, the company has remained essentially silent about its plans for its next-generation Mac operating system. The silence doesn’t mean that Apple hasn’t been working hard on the project since it first started showing up last fall.

As noted by AppleInsider, circumstantial evidence of Apple’s work showed up in a WebKit bug report early last month revealing that version of OS X 10.9 in testing was Build 13A451. According to Apple’s build number scheme, “13” refers to OS X 10.9, “A” refers to the 10.9.0 version, and “451” is part of a sequential numbering of compiled builds. It is currently being speculated that the relatively advanced “451” build number as of early May could indicate that Apple would be able to deliver a fairly mature version of OS X 10.9 to developers at its Worldwide Developers Conference next week, although there is no formal evidence for such a claim.

The initial developer preview of OS X Mountain Lion arrived as Build 12A128p in February 2012, with Apple releasing several additional builds to developers before releasing it to the public as Build 12A269 in July of that year. OS X Lion apparently spent a longer time in development but a similar amount of time in developer testing, originally beginning developer seeding with Build 11A390 in February 2011 before having launched to the public as Build 11A511 roughly five months later.

The Cupertino California company indicated when it launched that its first developer preview of OS X Mountain Lion last year that it was shifting to a more rapid yearly development cycle for OS X in order to bring more features to consumers at a faster rate. With Apple yet to have begun seeding developers with versions of OS X 10.9 and the company reportedly having pulled engineers from OS X to work on iOS 7, there have been several questions about how closely Apple will be able to stick to its yearly release plan. Ultimately we’ll have to wait and see.

While a new version of the thunderbolt is nice, there are so few referrals to use with it it has little benefit
I realize Intel is being careful to have manufacturers only make quality accessories the adoption of it is so slow it's ridiculous
That's just my opinion

Thunderbolt 1 adoption is going so slow releasing thunderbolt 2 would be pointless.

I don't think it would be pointless. Thunderbolt 2 allows transfers of 4k resolutions. While 4k monitors aren't that popular right now, in 5 years the prices will begin to drop and you will see more 4k options out in the world. Apple likes to stay current and since laptops last about 5 years, there would be no reason they wouldn't ingrate it now except for the fact that intel didn't build it into the first batch of haswell processors.

I don't think it would be pointless. Thunderbolt 2 allows transfers of 4k resolutions. While 4k monitors aren't that popular right now, in 5 years the prices will begin to drop and you will see more 4k options out in the world. Apple likes to stay current and since laptops last about 5 years, there would be no reason they wouldn't ingrate it now except for the fact that intel didn't build it into the first batch of haswell processors.

I guess, but IMO laptops last only 2-3 years, desktops last 5-6 though